With ceramic crucibles in which metals are to be melted, one problem consists in that they indeed have a high melting temperature but in some cases they react with the melt or that pieces detach from the brittle crucible ceramic and float as inclusions in the melt. In contrast, crucibles of metal often do not tolerate the high melting temperatures without special measures
In order to be able to melt materials with high melting temperatures in crucibles with relatively low melting temperatures, it is known to cool the crucibles with water so that they are kept at a temperature below their own melting points. However, now the melting material is cooled down relatively strongly because it is in contact with the cooled crucible.
A melting material with high temperature can be readily heated in a water-cooled metal crucible by means of inductive heating above the melting temperature of the crucible. Herein however, the problem of eddy current formation in the crucible occurs.
To decrease the eddy current losses caused hereby it is known to subdivide the crucible in many segments separated from each other by an insulating layer (DEP 518 499; USP 3 775 091, EP-A-0 276 544).
A fundamental disadvantage of the known cooled crucibles comprises in the high electrical losses which result from the eddy currents in the crucible wall and in the high heat losses which result from the heat flow from the melt into the cooled crucible wall. The herefrom resulting efficiency of the process can only be kept at an acceptable magnitude thereby that the melting process takes place at the maximum possible rate.
The invention therefore is based on the task of creating a cooled ceramic-free induction crucible with low electrical losses.